bq27531-G1 Battery Management Unit Impedance Track · PDF filePROTECTION IC FETs Single Cell...

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An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,intellectual property matters and other important disclaimers. PRODUCTION DATA.

bq27531-G1SLUSBE7C –MARCH 2013–REVISED JANUARY 2016

bq27531-G1 Battery Management Unit Impedance Track™ Fuel Gauge With MaxLife™Technology for Use With the bq2419x Charger Controller

1

1 Features1• Battery Fuel Gauge and Charger Controller for 1-

Cell Li-Ion Applications• Resides on System Main Board• Battery Fuel Gauge Based on Patented

Impedance Track™ Technology– Models the Battery Discharge Curve for

Accurate Time-to-Empty Predictions– Automatically Adjusts for Battery Aging,

Battery Self-Discharge, and Temperature/RateInefficiencies

– Low-Value Sense Resistor (5 mΩ to 20 mΩ)• Battery Charger Controller With Customizable

Charge Profiles– Configurable Charge Voltage and Current

Based on Temperature– Optional State of Health (SoH) and Multilevel-

Based Charge Profiles• Host-Free Autonomous Battery Management

System– Reduced Software Overhead Allows for Easy

Portability Across Platforms and Shorter OEMDesign Cycles

– Higher Safety and Security• Intelligent Charging—Customized and Adaptive

Charging Profiles– Charger Control Based on SoH– Temperature Level Charging (TLC)

• Battery Charger Controller for bq2419x Single-CellSwitched-Mode Battery Charger– Stand-Alone Charging Solution– SHIP Mode Capability

• 400-kHz I2C Interface for Connection to SystemMicrocontroller Port

• In a 15-Pin NanoFree™ Packaging

2 Applications• Smart Phones, Feature Phones, and Tablets• Digital Still and Video Cameras• Handheld Terminals• MP3 or Multimedia Players

3 DescriptionThe Texas Instruments bq27531-G1 system-side Li-Ion Battery Management Unit is a microcontrollerperipheral that provides Impedance Track fuelgauging and charging control for single-cell Li-Ionbattery packs. The device requires little systemmicrocontroller firmware development. Together withthe bq2419x Single-Cell Switched-Mode Charger, thebq27531-G1 manages an embedded battery(nonremovable) or a removable battery pack.

The bq27531-G1 uses the patented Impedance Trackalgorithm for fuel gauging, and provides informationsuch as remaining battery capacity (mAh), state-of-charge (%), run time to empty (minimum), batteryvoltage (mV), temperature (°C), and state of health(%).

Battery fuel gauging with the bq27531-G1 requiresonly PACK+ (P+), PACK– (P–), and Thermistor (T)connections to a removable battery pack orembedded battery circuit. The CSP option is a 15-pinpackage in the dimensions of 2.61 mm × 1.96 mmwith a 0.5-mm lead pitch, which is ideal for space-constrained applications.

Device Information(1)

PART NUMBER PACKAGE BODY SIZE (NOM)bq27531-G1 DSBGA (15) 2.61 mm × 1.96 mm

(1) For all available packages, see the orderable addendum atthe end of the data sheet.

Simplified Schematic

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Table of Contents1 Features .................................................................. 12 Applications ........................................................... 13 Description ............................................................. 14 Revision History..................................................... 25 Device Options....................................................... 36 Pin Configuration and Functions ......................... 37 Specifications......................................................... 4

7.1 Absolute Maximum Ratings ...................................... 47.2 ESD Ratings.............................................................. 47.3 Recommended Operating Conditions....................... 47.4 Thermal Information .................................................. 47.5 Electrical Characteristics: Supply Current................. 57.6 Digital Input and Output DC Characteristics ............. 57.7 Power-On Reset........................................................ 57.8 2.5-V LDO Regulator ................................................ 57.9 Internal Clock Oscillators .......................................... 57.10 ADC (Temperature and Cell Measurement)

Characteristics ........................................................... 67.11 Integrating ADC (Coulomb Counter)

Characteristics ........................................................... 67.12 Data Flash Memory Characteristics........................ 67.13 I2C-Compatible Interface Communication Timing

Characteristics ........................................................... 7

7.14 Typical Characteristics ............................................ 88 Detailed Description .............................................. 9

8.1 Overview ................................................................... 98.2 Functional Block Diagram ....................................... 108.3 Feature Description................................................. 118.4 Device Functional Modes........................................ 128.5 Programming........................................................... 16

9 Application and Implementation ........................ 219.1 Application Information............................................ 219.2 Typical Application ................................................. 21

10 Power Supply Recommendations ..................... 2610.1 Power Supply Decoupling..................................... 26

11 Layout................................................................... 2611.1 Layout Guidelines ................................................. 2611.2 Layout Example .................................................... 27

12 Device and Documentation Support ................. 2812.1 Documentation Support ........................................ 2812.2 Community Resources.......................................... 2812.3 Trademarks ........................................................... 2812.4 Electrostatic Discharge Caution............................ 2812.5 Glossary ................................................................ 28

13 Mechanical, Packaging, and OrderableInformation ........................................................... 28

4 Revision History

Changes from Revision B (September 2015) to Revision C Page

• Changed ESD Ratings ........................................................................................................................................................... 4

Changes from Revision A (June 2015) to Revision B Page

• Changed a Pin Functions description to correct the TRM link ............................................................................................... 3• Changed Figure 6 ................................................................................................................................................................ 13• Added Figure 7 .................................................................................................................................................................... 14


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(TOP VIEW)

D1

D2

D3

E1

E2

E3

C1

C2

C3

B1

B2

B3

A1

A2

A3

D1

D2

D3

E1

E2

E3

C1

C2

C3

B1

B2

B3

A1

A2

A3

(BOTTOM VIEW)

Dxxxx

MIN TYP MAXDIM UNITS

2580 2610 2640Dm

1926 1956 1986E

Pin A1Index Area

E

3

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5 Device Options

PART NUMBER FIRMWAREVERSION

COMMUNICATIONFORMAT

bq27531YZFR-G1 1.02(0x0102) I2C

bq27531YZFT-G1

(1) I/O = Digital input/output, IA = Analog input, P = Power connection

6 Pin Configuration and Functions

YZF Package15-Pin DSBGA

Pin FunctionsPIN

I/O (1) DESCRIPTIONNAME NO.

BAT E2 I Cell voltage measurement input. ADC input. Recommend 4.8 V maximum for conversion accuracy.

BI/TOUT E3 I/O Battery insertion detection input. Power pin for pack thermistor network. Thermistor multiplexer control pin. Use withpullup resistor >1 MΩ (1.8 MΩ typical).

BSDA C3 I/O Battery Charger data line for chipset communication. Push-pull output.

BSCL B2 O Battery Charger clock output line for chipset communication. Push-pull output.

CE D2 I Chip Enable. Internal LDO is disconnected from REGIN when driven low. Note: CE has an internal ESD protectiondiode connected to REGIN. Recommend maintaining VCE ≤ VREGIN under all conditions.

REGIN E1 P Regulator input. Decouple with 0.1-μF ceramic capacitor to Vss.

SCL A3 I Slave I2C serial communications clock input line for communication with system (Master). Open-drain I/O. Use with10-kΩ pullup resistor (typical).

SDA B3 I/O Slave I2C serial communications data line for communication with system (Master). Open-drain I/O. Use with 10-kΩpullup resistor (typical).

SOC_INT A2 I/O SOC state interrupts output. Generates a pulse as described in the bq27531-G1 Technical Reference Manual(SLUUA96). Open-drain output.

SRN B1 IA Analog input pin connected to the internal coulomb counter where SRN is nearest the Vss connection. Connect to 5-mΩ to 20-mΩ sense resistor.

SRP A1 IA Analog input pin connected to the internal coulomb counter where SRP is nearest the PACK– connection. Connect to5-mΩ to 20-mΩ sense resistor.

TS D3 IA Pack thermistor voltage sense (use 103AT-type thermistor). ADC input.

VCC D1 P Regulator output and bq27531-G1 power. Decouple with 1-μF ceramic capacitor to Vss.

VSS C1, C2 P Device ground


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4




(1) Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratingsonly, which do not imply functional operation of the device at these or any other conditions beyond those indicated under RecommendedOperating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.

(2) Condition not to exceed 100 hours at 25°C lifetime.

7 Specifications

7.1 Absolute Maximum Ratingsover operating free-air temperature range (unless otherwise noted) (1)

MIN MAX UNIT

VREGIN Regulator input–0.3 5.5

V–0.3 6.0 (2)

VCE CE input pin –0.3 VREGIN + 0.3 VVCC Supply voltage –0.3 2.75 VVIOD Open-drain I/O pins (SDA, SCL, SOC_INT) –0.3 5.5 V

VBAT BAT input pin–0.3 5.5

V–0.3 6.0 (2)

VIInput voltage to all other pins(BI/TOUT, TS, SRP, SRN, BSDA, BSCL) –0.3 VCC + 0.3 V

TA Operating free-air temperature –40 85 °C

(1) JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.(2) JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process.

7.2 ESD RatingsVALUE UNIT

V(ESD)Electrostaticdischarge

Human body model (HBM), per ANSI/ESDA/JEDEC JS-001, BAT pin (1) ±1500VHuman-body model (HBM), per ANSI/ESDA/JEDEC JS-001), All other pins (1) ±2000

Charged device model (CDM), per JEDEC specification JESD22-C101 (2) ±250

7.3 Recommended Operating ConditionsTA = –40°C to 85°C, VREGIN = VBAT = 3.6 V (unless otherwise noted)

MIN NOM MAX UNIT

VREGIN Supply voltageNo operating restrictions 2.8 4.5

VNo flash writes 2.45 2.8

CREGINExternal input capacitor for internal LDObetween REGIN and VSS Nominal capacitor values specified.

Recommend a 5% ceramic X5R typecapacitor located close to the device.

0.1 μF

CLDO25External output capacitor for internal LDObetween VCC and VSS

0.47 1 μF

tPUCD Power-up communication delay 250 ms

(1) For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics applicationreport, SPRA953.

7.4 Thermal Information

THERMAL METRIC (1)bq27531-G1

UNITYZF [DSBGA]15 PINS

RθJA Junction-to-ambient thermal resistance 70 °C/WRθJC(top) Junction-to-case(top) thermal resistance 17 °C/WRθJB Junction-to-board thermal resistance 20 °C/WψJT Junction-to-top characterization parameter 1 °C/WψJB Junction-to-board characterization parameter 18 °C/WRθJC(bot) Junction-to-case(bottom) thermal resistance N/A °C/W


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(1) Specified by design. Not production tested.

7.5 Electrical Characteristics: Supply CurrentTA = 25°C and VREGIN = VBAT = 3.6 V (unless otherwise noted)

PARAMETER TEST CONDITIONS MIN TYP MAX UNIT

ICC(1) NORMAL operating mode current Fuel gauge in NORMAL mode

ILOAD > Sleep current 118 μA

ISLP+(1) SLEEP+ operating mode current Fuel gauge in SLEEP+ mode

ILOAD < Sleep current 62 μA

ISLP(1) Low-power storage mode current Fuel gauge in SLEEP mode

ILOAD < Sleep current 23 μA

IHIB(1) HIBERNATE operating mode current Fuel gauge in HIBERNATE mode

ILOAD < Hibernate current 8 μA


7.6 Digital Input and Output DC CharacteristicsTA = –40°C to 85°C, typical values at TA = 25°C and VREGIN = 3.6 V (unless otherwise noted)

PARAMETER TEST CONDITIONS MIN TYP MAX UNIT

VOLOutput voltage, low (SCL, SDA,SOC_INT, BSDA, BSCL) IOL = 3 mA 0.4 V

VOH(PP) Output voltage, high (BSDA, BSCL) IOH = –1 mA VCC – 0.5V

VOH(OD)Output voltage, high (SDA, SCL,SOC_INT)

External pullup resistor connected toVCC

VCC – 0.5

VILInput voltage, low (SDA, SCL) –0.3 0.6

VInput voltage, low (BI/TOUT) BAT INSERT CHECK mode active –0.3 0.6

VIHInput voltage, high (SDA, SCL) 1.2

VInput voltage, high (BI/TOUT) BAT INSERT CHECK mode active 1.2 VCC + 0.3

VIL(CE) Input voltage, low (CE)VREGIN = 2.8 V to 4.5 V

0.8V

VIH(CE) Input voltage, high (CE) 2.65Ilkg

(1) Input leakage current (I/O pins) 0.3 μA

7.7 Power-On ResetTA = –40°C to 85°C, typical values at TA = 25°C and VREGIN = 3.6 V (unless otherwise noted)

PARAMETER TEST CONDITIONS MIN TYP MAX UNITVIT+ Positive-going battery voltage input at

VCC2.05 2.15 2.20 V

VHYS Power-on reset hysteresis 115 mV

(1) LDO output current, IOUT, is the total load current. LDO regulator must be used to power internal fuel gauge only.

7.8 2.5-V LDO RegulatorTA = –40°C to 85°C, CLDO25 = 1 μF, VREGIN = 3.6 V (unless otherwise noted)

PARAMETER TEST CONDITION MIN TYP MAX UNIT

VREG25 Regulator output voltage (VCC)2.8 V ≤ VREGIN ≤ 4.5 V, IOUT ≤ 16 mA (1) 2.3 2.5 2.6

V2.45 V ≤ VREGIN < 2.8 V (low battery),IOUT ≤ 3mA 2.3

7.9 Internal Clock OscillatorsTA = –40°C to 85°C, 2.4 V < VCC < 2.6 V; typical values at TA = 25°C and VCC = 2.5 V (unless otherwise noted)

PARAMETER TEST CONDITIONS MIN TYP MAX UNITfOSC High-frequency oscillator 8.389 MHzfLOSC Low-frequency oscillator 32.768 kHz


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(1) Specified by design. Not tested in production.

7.10 ADC (Temperature and Cell Measurement) CharacteristicsTA = –40°C to 85°C, 2.4 V < VCC < 2.6 V; typical values at TA = 25°C and VCC = 2.5 V (unless otherwise noted)

PARAMETER TEST CONDITIONS MIN TYP MAX UNITVADC1 Input voltage (TS) VSS –

0.1252 V

VADC2 Input voltage (BAT) VSS –0.125

5 V

VIN(ADC) Input voltage 0.05 1 VGTEMP Internal temperature sensor voltage

gain–2 mV/°C

tADC_CONV Conversion time 125 msResolution 14 15 bits

VOS(ADC) Input offset 1 mVZADC1

(1) Effective input resistance (TS) 8 MΩ

ZADC2(1) Effective input resistance (BAT)

bq27531-G1 not measuring cell voltage 8 MΩbq27531-G1 measuring cell voltage 100 kΩ

Ilkg(ADC)(1) Input leakage current 0.3 μA

(1) Specified by design. Not tested in production.

7.11 Integrating ADC (Coulomb Counter) CharacteristicsTA = –40°C to 85°C, 2.4 V < VCC < 2.6 V; typical values at TA = 25°C and VCC = 2.5 V (unless otherwise noted)

PARAMETER TEST CONDITIONS MIN TYP MAX UNITVSR Input voltage,

V(SRP) and V(SRN)

VSR = V(SRP) – V(SRN) –0.125 0.125 V

tSR_CONV Conversion time Single conversion 1 sResolution 14 15 bits

VOS(SR) Input offset 10 μVINL Integral nonlinearity error ±0.007% ±0.034% FSRZIN(SR)

(1) Effective input resistance 2.5 MΩIlkg(SR)

(1) Input leakage current 0.3 μA


7.12 Data Flash Memory CharacteristicsTA = –40°C to 85°C, 2.4 V < VCC < 2.6 V; typical values at TA = 25°C and VCC = 2.5 V (unless otherwise noted)

PARAMETER TEST CONDITIONS MIN TYP MAX UNITtDR

(1) Data retention 10 YearsFlash-programming writecycles (1) 20000 Cycles

tWORDPROG(1) Word programming time 2 ms

ICCPROG(1) Flash-write supply current 5 10 mA

tDFERASE(1) Data flash master erase time 200 ms

tIFERASE(1) Instruction flash master erase

time 200 ms

tPGERASE(1) Flash page erase time 20 ms


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7




(1) If the clock frequency (fSCL) is > 100 kHz, use 1-byte write commands for proper operation. All other transactions types are supported at400 kHz. (See I2C Interface and I2C Command Waiting Time).

7.13 I2C-Compatible Interface Communication Timing CharacteristicsTA = –40°C to 85°C, 2.4 V < VCC < 2.6 V; typical values at TA = 25°C and VCC = 2.5 V (unless otherwise noted)

PARAMETER MIN NOM MAX UNITtr SCL/SDA rise time 300 nstf SCL/SDA fall time 300 nstw(H) SCL pulse duration (high) 600 nstw(L) SCL pulse duration (low) 1.3 μstsu(STA) Setup for repeated start 600 nstd(STA) Start to first falling edge of SCL 600 nstsu(DAT) Data setup time 100 nsth(DAT) Data hold time 0 nstsu(STOP) Setup time for stop 600 nst(BUF) Bus free time between stop and start 66 μsfSCL Clock frequency (1) 400 kHz

Figure 1. I2C-Compatible Interface Timing Diagrams


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Temperature (qC)

fLO

SC

- L

ow F

requ

ency

Osc

illat

or (

kHz)

-40 -20 0 20 40 60 80 10030

30.5

31

31.5

32

32.5

33

33.5

34

D003Temperature (qC)

Rep

orte

d T

empe

ratu

re E

rror

(qC

)

-30 -20 -10 0 10 20 30 40 50 60-5

-4

-3

-2

-1

0

1

2

3

4

5

D004

Temperature (qC)

VR

EG

25 -

Reg

ulat

or O

utpu

t Vol

tage

(V

)

2.35

2.4

2.45

2.5

2.55

2.6

2.65

D001

VREGIN = 2.7 VVREGIN = 4.5 V

Temperature (qC)

f OS

C -

Hig

h F

requ

ency

Osc

illat

or (

MH

z)

-40 -20 0 20 40 60 80 1008

8.1

8.2

8.3

8.4

8.5

8.6

8.7

8.8

D002

8




7.14 Typical Characteristics

Figure 2. Regulator Output Voltage vs Temperature Figure 3. High-Frequency Oscillator Frequency vsTemperature

Figure 4. Low-Frequency Oscillator Frequency vsTemperature

Figure 5. Reported Internal Temperature Measurement vsTemperature


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9




8 Detailed Description

8.1 OverviewThe fuel gauge accurately predicts the battery capacity and other operational characteristics of a single, Li-based, rechargeable cell. It can be interrogated by a system processor to provide cell information, such asremaining capacity and state-of-charge (SOC) as well as SOC interrupt signal to the host.

The fuel gauge can control a bq2419x Charger IC without the intervention from an application system processor.Using the bq27531-G1 and bq2419x chipset, batteries can be charged with the typical constant-current,constant-voltage (CCCV) profile or charged using a Multi-Level Charging (MLC) algorithm.

NOTEFormatting conventions used in this document:Commands: italics with parentheses and no breaking spaces, for example, Control()

Data flash: italics, bold, and breaking spaces, for example, Design CapacityRegister bits and flags: brackets and italics, for example, [TDA]

Data flash bits: brackets, italics and bold, for example, [LED1]Modes and states: ALL CAPITALS, for example, UNSEALED mode


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REGIN

BAT

VCC

TS

SRN

SRP

SOCINT SDA

VSS SCL

BSDA

MUX

4R

Data FLASH

LDO

DataSRAM

CC

ADC

2.5 V

R

Internal Temp

Sensor

Wake Comparator

Instruction FLASH

Instruction ROM

I2C Slave Engine

CPU

22

22

8 8I2C Master

Engine

HFO LFO

GP Timer and

PWM

I/O Controller

Wake and

Watchdog Timer

HFO

HFO/128

HFO/128

HFO/4

POR

BSCL

BI/TOUT

10




8.2 Functional Block Diagram


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11




8.3 Feature DescriptionInformation is accessed through a series of commands, called Standard Commands. Further capabilities areprovided by the additional Extended Commands set. Both sets of commands, indicated by the general formatCommand(), are used to read and write information contained within the control and status registers, as well asits data flash locations. Commands are sent from system to gauge using the I2C serial communications engine,and can be executed during application development, pack manufacture, or end-equipment operation.

Cell information is stored in nonvolatile flash memory. Many of these data flash locations are accessible duringapplication development. They cannot, generally, be accessed directly during end-equipment operation. Accessto these locations is achieved by either use of the companion evaluation software, through individual commands,or through a sequence of data-flash access commands. To access a desired data flash location, the correct dataflash subclass and offset must be known.

The key to the high-accuracy gas gauging prediction is the TI proprietary Impedance Track algorithm. Thisalgorithm uses cell measurements, characteristics, and properties to create SOC predictions that can achieveless than 1% error across a wide variety of operating conditions and over the lifetime of the battery.

The fuel gauge measures the charging and discharging of the battery by monitoring the voltage across a small-value series sense resistor (5 to 20 mΩ, typical) located between the system VSS and the battery PACK–terminal. When a cell is attached to the fuel gauge, cell impedance is computed, based on cell current, cell open-circuit voltage (OCV), and cell voltage under loading conditions.

The external temperature sensing is optimized with the use of a high-accuracy negative temperature coefficient(NTC) thermistor with R25 = 10.0 kΩ ±1%, B25/85 = 3435 K ±1% (such as Semitec NTC 103AT). The fuel gaugecan also be configured to use its internal temperature sensor. When an external thermistor is used, a 18.2-kΩpullup resistor between the BI/TOUT and TS pins is also required. The fuel gauge uses temperature to monitorthe battery-pack environment, which is used for fuel gauging and cell protection functionality.

To minimize power consumption, the fuel gauge has different power modes: NORMAL, SLEEP, SLEEP+,HIBERNATE, and BAT INSERT CHECK. The fuel gauge passes automatically between these modes, dependingupon the occurrence of specific events, though a system processor can initiate some of these modes directly.

For complete operational details, see the bq27531-G1 Technical Reference Manual (SLUUA96).

8.3.1 Functional DescriptionThe fuel gauge measures the cell voltage, temperature, and current to determine battery SOC. The fuel gaugemonitors the charging and discharging of the battery by sensing the voltage across a small-value resistor (5 mΩto 20 mΩ, typical) between the SRP and SRN pins and in series with the cell. By integrating charge passingthrough the battery, the battery SOC is adjusted during battery charge or discharge.

The total battery capacity is found by comparing states of charge before and after applying the load with theamount of charge passed. When an application load is applied, the impedance of the cell is measured bycomparing the OCV obtained from a predefined function for present SOC with the measured voltage under load.Measurements of OCV and charge integration determine chemical SOC and chemical capacity (Qmax). Theinitial Qmax values are taken from a cell manufacturer's data sheet multiplied by the number of parallel cells. It isalso used for the value in Design Capacity. The fuel gauge acquires and updates the battery-impedance profileduring normal battery usage. It uses this profile, along with SOC and the Qmax value, to determineFullChargeCapacity() and StateOfCharge(), specifically for the present load and temperature.FullChargeCapacity() is reported as capacity available from a fully-charged battery under the present load andtemperature until Voltage() reaches the Terminate Voltage. NominalAvailableCapacity() andFullAvailableCapacity() are the uncompensated (no or light load) versions of RemainingCapacity() andFullChargeCapacity(), respectively.

The fuel gauge has two flags accessed by the Flags() function that warn when the battery SOC has fallen tocritical levels. When RemainingCapacity() falls below the first capacity threshold as specified in SOC1 SetThreshold, the [SOC1] (State of Charge Initial) flag is set. The flag is cleared once RemainingCapacity() risesabove SOC1 Clear Threshold.

When the voltage is discharged to Terminate Voltage, the SOC will be set to 0.


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12




8.4 Device Functional Modes

8.4.1 Power ModesThe fuel gauge has different power modes:• BAT INSERT CHECK: The BAT INSERT CHECK mode is a powered-up, but low-power halted, state where

the fuel gauge resides when no battery is inserted into the system.• NORMAL: In NORMAL mode, the fuel gauge is fully powered and can execute any allowable task.• SLEEP: In SLEEP mode, the fuel gauge turns off the high-frequency oscillator and exists in a reduced- power

state, periodically taking measurements and performing calculations.• SLEEP+: In SLEEP+ mode, both low-frequency and high-frequency oscillators are active. Although the

SLEEP+ mode has higher current consumption than the SLEEP mode, it is also a reduced power mode.• HIBERNATE: In HIBERNATE mode, the fuel gauge is in a low power state, but can be woken up by

communication or certain I/O activity.

The relationship between these modes is shown in Figure 6 and Figure 7.

8.4.1.1 BAT INSERT CHECK ModeThis mode is a halted-CPU state that occurs when an adapter, or other power source, is present to power thefuel gauge (and system), yet no battery has been detected. When battery insertion is detected, a series ofinitialization activities begin, which include: OCV measurement, setting the Flags() [BAT_DET] bit, and selectingthe appropriate battery profiles.

Some commands, issued by a system processor, can be processed while the fuel gauge is halted in this mode.The gauge wakes up to process the command, then returns to the halted state awaiting battery insertion.

8.4.1.2 NORMAL ModeThe fuel gauge is in NORMAL mode when not in any other power mode. During this mode, AverageCurrent() ,Voltage() , and Temperature() measurements are taken, and the interface data set is updated. Decisions tochange states are also made. This mode is exited by activating a different power mode.

Because the gauge consumes the most power in NORMAL mode, the Impedance Track algorithm minimizes thetime the fuel gauge remains in this mode.

8.4.1.3 SLEEP ModeSLEEP mode is entered automatically if the feature is enabled (Op Config [SLEEP] = 1) and AverageCurrent()is below the programmable level Sleep Current. Once entry into SLEEP mode has been qualified, but prior toentering it, the fuel gauge performs a coulomb counter autocalibration to minimize offset.

During SLEEP mode, the fuel gauge periodically takes data measurements and updates its data set. However, amajority of its time is spent in an idle condition.

The fuel gauge exits SLEEP mode if any entry condition is broken, specifically when:• AverageCurrent() rises above Sleep Current, or• A current in excess of IWAKE through RSENSE is detected.

In the event that a battery is removed from the system while a charger is present (and powering the gauge),Impedance Track updates are not necessary. Hence, the fuel gauge enters a state that checks for batteryinsertion and does not continue executing the Impedance Track algorithm.


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POR

BAT INSERT CHECK

Check for battery insertionfrom HALT state.

No gauging

System Sleep

SLEEP+

SLEEP

Fuel gauging and dataupdated every 20 seconds.Both LFO and HFO are ON.

Entry to SLEEP[SNOOZE] = 0CONTROL_STATUS

Exit From HIBERNATEBattery Removed

NORMAL

Fuel gauging and dataupdated every second

Exit From HIBERNATECommunication Activity

AND Comm address is for bq27531

= 0Recommend Host also set

= 0

bq27531 clears CONTROL_STATUS[HIBERNATE]

CONTROL_STATUS[HEBERNATE]

Entry To NORMAL[BAT_DET] = 1Flags

Flags [BAT_DET] = 0

Fuel gauging and dataupdated every 20 seconds.(LFO ON and HFO OFF)

Exit From SLEEPHost has set

= 1OR

CONTROL_STATUS[HIBERNATE]

V <CELL Hibernate Voltage

To WAIT_HIBERNATE

Entry to SLEEP+[SNOOZE] = 1CONTROL_STATUS

Exit From SLEEP>

ORCurrent is detected above

Ι Ι

Ι

AverageCurrent ( ) Sleep Current

WAKE

Exit From SLEEP+Any communication to the gauge

OR>

ORCurrent is detected above

Ι Ι

Ι

AverageCurrent ( ) Sleep Current

WAKE

Exit From NORMAL[BAT_DET] = 0Flags

Exit From WAIT_HIBERNATEHost must set

= 0AND



Entry To SLEEP+= 1

AND= 1]

Operation Configuration [SLEEP]

CONTROL_STAUS [SNOOZE]AND

Ι ΙAverageCurrent ( ) < Sleep Current

Entry To SLEEP+= 1Operation Configuration [SLEEP]

AND

AND= 0

Ι ΙAverageCurrent ( )

CONTROL_STAUS [SNOOZE]

< Sleep Current

Exit From SLEEP[BAT_DET] = 0Flags

13




Device Functional Modes (continued)

Figure 6. Power Mode Diagram—System Sleep


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System Shutdown

HIBERNATE

Disable all bq27531subcircuits.

WAIT_HIBERNATE

Fuel gauging and dataupdated every 20 seconds.

Wakeup From HIBERNATECommunication Activity

ANDComm address is not for

bq27531

Exit From WAIT_HIBERNATECell relaxed

ANDAverageCurrent () <

ORCell relaxed

ANDV <

Ι Ι HibernateCurrent

Hibernate VoltageCELL

To SLEEP

POR

BAT INSERT CHECK

Check for battery insertionfrom HALT state.

No gauging

NORMAL

Fuel gauging and dataupdated every second.

Entry To NORMAL[BAT_DET] = 1Flags

Exit From WAIT_HIBERNATEHost must set

= 0AND



Exit From SLEEPHost has set

= 1OR



Flags [BAT_DET] = 0

Exit From NORMAL[BAT_DET] = 0Flags

Exit From SLEEP[BAT_DET] = 0Flags

Exit From HIBERNATEBattery Removed

Exit From HIBERNATECommunication Activity

AND Comm address is for bq27531

= 0Recommend Host also set

= 0

bq27531 clears CONTROL_STATUS[HIBERNATE]

CONTROL_STATUS[HEBERNATE]

14




Device Functional Modes (continued)

Figure 7. Power Mode Diagram—System Shutdown


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15




Device Functional Modes (continued)8.4.2 SLEEP+ ModeCompared to the SLEEP mode, SLEEP+ mode has the high-frequency oscillator in operation. Thecommunication delay could be eliminated. The SLEEP+ mode is entered automatically if the feature is enabled(CONTROL_STATUS [SNOOZE] = 1) and AverageCurrent() is below the programmable level Sleep Current.During SLEEP+ mode, the fuel gauge periodically takes data measurements and updates its data set. However,a majority of its time is spent in an idle condition.

The fuel gauge exits SLEEP+ mode if any entry condition is broken, specifically when:• Any communication activity with the gauge, or• AverageCurrent() rises above Sleep Current , or• A current in excess of IWAKE through RSENSE is detected.

8.4.3 HIBERNATE ModeHIBERNATE mode should be used when the system equipment needs to enter a low-power state, and minimalgauge power consumption is required. This mode is ideal when system equipment is set to its own HIBERNATE,SHUTDOWN, or OFF mode.

Before the fuel gauge can enter HIBERNATE mode, the system must set the CONTROL_STATUS[HIBERNATE] bit. The gauge waits to enter HIBERNATE mode until it has taken a valid OCV measurement andthe magnitude of the average cell current has fallen below Hibernate Current. The gauge can also enterHIBERNATE mode if the cell voltage falls below Hibernate Voltage and a valid OCV measurement has beentaken. The gauge remains in HIBERNATE mode until the system issues a direct I 2 C command to the gauge ora POR occurs. Any I 2 C communication that is not directed to the gauge does not wake the gauge.

It is the responsibility of the system to wake the fuel gauge after it has gone into HIBERNATE mode. Afterwaking, the gauge can proceed with the initialization of the battery information (OCV, profile selection, and soforth).


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16




(1) Only writeable when Charger Options [BYPASS] is set.

8.5 Programming

8.5.1 Data Commands

8.5.1.1 Standard Data CommandsThe bq27531-G1 uses a series of 2-byte standard commands to enable system reading and writing of batteryinformation. Each standard command has an associated command-code pair, as indicated in Table 1. Becauseeach command consists of two bytes of data, two consecutive I2C transmissions must be executed both toinitiate the command function, and to read or write the corresponding two bytes of data. Additional details arefound in the bq27531-G1 Technical Reference Manual (SLUUA96).

Table 1. Standard Commands

NAME COMMAND CODE UNIT SEALEDACCESS

UNSEALEDACCESS

Control() 0x00 and 0x01 NA R/W R/WAtRate() 0x02 and 0x03 mA R/W R/WAtRateTimeToEmpty() 0x04 and 0x05 Minutes R R/WTemperature() 0x06 and 0x07 0.1 K R/W R/WVoltage() 0x08 and 0x09 mV R R/WFlags() 0x0A and 0x0B Hex R R/WNominalAvailableCapacity() 0x0C and 0x0D mAh R R/WFullAvailableCapacity() 0x0E and 0x0F mAh R R/WRemainingCapacity() 0x10 and 0x11 mAh R R/WFullChargeCapacity() 0x12 and 0x13 mAh R R/WAverageCurrent() 0x14 and 0x15 mA R R/WTimeToEmpty() 0x16 and 0x17 Minutes R R/WRemainingCapacityUnfiltered() 0x18 and 0x19 mAh R R/WStandbyCurrent() 0x1A and 0x1B mA R R/WRemainingCapacityFiltered() 0x1C and 0x1D mAh R R/WProgChargingCurrent() 0x1E and 0x1F mA R (1) R (1)

ProgChargingVoltage() 0x20 and 0x21 mV R (1) R (1)

FullChargeCapacityUnfiltered() 0x22 and 0x23 mAh R R/WAveragePower() 0x24 and 0x25 mW R R/WFullChargeCapacityFiltered() 0x26 and 0x27 mAh R R/WStateOfHealth() 0x28 and 0x29 %/num R R/WCycleCount() 0x2A and 0x2B Counters R R/WStateOfCharge() 0x2C and 0x2D % R R/WTrueSOC() 0x2E and 0x2F % R R/WInstantaneousCurrentReading() 0x30 and 0x31 mA R R/WInternalTemperature() 0x32 and 0x33 0.1 K R R/WChargingLevel() 0x34 and 0x35 Num R RLevelTaperCurrent() 0x6E and 0x6F mA R RCalcChargingCurrent() 0x70 and 0x71 mA R RCalcChargingVoltage() 0x72 and 0x73 V R R


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17




8.5.1.1.1 Control(): 0x00/0x01

Issuing a Control() command requires a subsequent 2-byte subcommand. These additional bytes specify theparticular control function desired. The Control() command allows the system to control specific features of thebq27531-G1 during normal operation and additional features when the device is in different access modes, asdescribed in Table 2. Additional details are found in the bq27531-G1 Technical Reference Manual (SLUUA96).

Table 2. Control() Subcommands

CNTL FUNCTION CNTLDATA

SEALEDACCESS DESCRIPTION

CONTROL_STATUS 0x0000 Yes Reports the status of hibernate, IT, and so forthDEVICE_TYPE 0x0001 Yes Reports the device type (for example, 0x0531 for bq27531)FW_VERSION 0x0002 Yes Reports the firmware version on the device typeHW_VERSION 0x0003 Yes Reports the hardware version of the device typePREV_MACWRITE 0x0007 Yes Returns previous MAC subcommand codeCHEM_ID 0x0008 Yes Reports the chemical identifier of the Impedance Track configurationBOARD_OFFSET 0x0009 No Forces the device to measure and store the board offsetCC_OFFSET 0x000a No Forces the device to measure the internal CC offsetCC_OFFSET_SAVE 0x000b No Forces the device to store the internal CC offsetOCV_CMD 0x000c Yes Request the gauge to take a OCV measurementBAT_INSERT 0x000d Yes Forces the BAT_DET bit set when the [BIE] bit is 0BAT_REMOVE 0x000e Yes Forces the BAT_DET bit clear when the [BIE] bit is 0SET_HIBERNATE 0x0011 Yes Forces CONTROL_STATUS [HIBERNATE] to 1CLEAR_HIBERNATE 0x0012 Yes Forces CONTROL_STATUS [HIBERNATE] to 0SET_SLEEP+ 0x0013 Yes Forces CONTROL_STATUS [SNOOZE] to 1CLEAR_SLEEP+ 0x0014 Yes Forces CONTROL_STATUS [SNOOZE] to 0OTG_ENABLE 0x0015 Yes Commands the bq2419x into USB On The Go modeOTG_DISABLE 0x0016 Yes Disables OTG mode at the bq2419x

DIV_CUR_ENABLE 0x0017 Yes Makes the programmed charge current to be half of what is calculatedby the gauge charging algorithm.

CHG_ENABLE 0x001A Yes Enable charger. Charge will continue as dictated by gauge chargingalgorithm.

CHG_DISABLE 0x001B Yes Disable charger (Set CE bit of bq2419x)

GG_CHGRCTL_ENABLE 0x001C Yes Enables the gas gauge to control the charger while continuouslyresetting the charger watchdog

GG_CHGRCTL_DISABLE 0x001D Yes The gas gauge stops resetting the charger watchdog

DIV_CUR_DISABLE 0x001E Yes Makes the programmed charge current to be same as what iscalculated by the gauge charging algorithm.

DF_VERSION 0x001F Yes Returns the data flash versionSEALED 0x0020 No Places device in SEALED access modeIT_ENABLE 0x0021 No Enables the Impedance Track algorithmRESET 0x0041 No Forces a full reset of the bq27531-G1

SHIPMODE_ENABLE 0x0050 YesCommands the bq2419x to turn off BATFET after a delay timeprogrammed in data flash so that system load does not draw powerfrom battery

SHIPMODE_DISABLE 0x0051 YesCommands the bq2419x to disregard turning off BATFET before delaytime or turns on commands BATFET to turn on if an VBUS had powerduring the SHIPMODE enabling process


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18




8.5.1.2 Charger Data CommandsThe charger registers are mapped to a series of single byte Charger Data Commands to enable system readingand writing of battery charger registers. During charger power up, the registers are initialized to Charger ResetState. The fuel gauge can change the values of these registers during the System Reset State.

Each of the bits in the Charger Data Commands can be read/write. It is important to note that System Accesscan be different from the read/write access as defined in bq2419x charger hardware. The fuel gauge may blockwrite access to the charger hardware when the bit function is controlled by the fuel gauge exclusively. Forexample, the [VREGx] bits of Chrgr_Voltage_Reg4 are controlled by the fuel gauge and cannot be modified bysystem.

The bq27531 reads the corresponding registers of System_Stat_Reg8() and Fault_Reg9() every second to mirrorthe charger status. Other registers in the bq2419x are read when registers are modified by the bq27531.

Table 3. Charger Data Commands

NAME COMMAND CODEbq2419x

CHARGERMEMORY

LOCATION

SEALEDACCESS

UNSEALEDACCESS REFRESH RATE

ChargerStatus() CHGRSTAT 0x74 NA R R Every secondChrgr_InCtrl_Reg0() CHGR0 0x75 0x00 R/W R/W Data ChangeChrgr_POR_Config_Reg1() CHGR1 0x76 0x01 R/W R/W Data ChangeChrgr_Current_Reg2() CHGR2 0x77 0x02 R/W R/W Data ChangeChrgr_PreTerm_Reg3() CHGR3 0x78 0x03 R/W R/W Data ChangeChrgr_Voltage_Reg4() CHGR4 0x79 0x04 R/W R/W Data ChangeChrgr_TermTimer_Reg5() CHGR5 0x7a 0x05 R/W R/W Data ChangeChrgr_IRThermal_Reg6() CHGR6 0x7b 0x06 R/W R/W Data ChangeChrgr_OpCtrl_Reg7() CHGR7 0x7c 0x07 R/W R/W Data ChangeChrgr_Status_Reg8() CHGR8 0x7d 0x08 R/W R/W Every SecondChrgr_Fault_Reg9() CHGR9 0x7e 0x09 R/W R/W Every SecondChrgr_Rev_RegA() CHGRA 0x7f 0x0a R/W R/W Data Change


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Host generated

A AS 0ADDR[6:0] CMD[7:0] Sr 1ADDR[6:0] A DATA [7:0] A DATA [7:0] PN. . .

(d) incremental read

A AS 0ADDR[6:0] CMD[7:0] Sr 1ADDR[6:0] A DATA [7:0] PN

(c) 1- byte read

A AS A0 PADDR[6:0] CMD[7:0] DATA [7:0]

(a) 1-byte write (b) quick read

S 1ADDR[6:0] A DATA [7:0] PN

Gauge generated

. . .A AS A0 PADDR[6:0] CMD[7:0] DATA [7:0] DATA [7:0] A A

(e) incremental write

(S = Start , Sr = Repeated Start , A = Acknowledge , N = No Acknowledge , and P = Stop).

19




8.5.2 Communications

8.5.2.1 I2C InterfaceThe fuel gauge supports the standard I2C read, incremental read, quick read, one-byte write, and incrementalwrite functions. The 7-bit device address (ADDR) is the most significant 7 bits of the hex address and is fixed as1010101. The first 8 bits of the I2C protocol are, therefore, 0xAA or 0xAB for write or read, respectively.

Figure 8. Supported I2C Formats

The quick read returns data at the address indicated by the address pointer. The address pointer, a registerinternal to the I2C communication engine, increments whenever data is acknowledged by the bq27531-G1 or theI2C master. “Quick writes” function in the same manner and are a convenient means of sending multiple bytes toconsecutive command locations (such as two-byte commands that require two bytes of data).

The following command sequences are not supported:Attempt to write a read-only address (NACK after data sent by master):

Figure 9. Attempt to Write a Read-Only Address

Attempt to read an address above 0x6B (NACK command):

Figure 10. Attempt to Read an Address Above 0x6B

8.5.2.2 I2C Time-OutThe I2C engine releases both SDA and SCL if the I2C bus is held low for 2 seconds. If the bq27531-G1 is holdingthe lines, releasing them frees them for the master to drive the lines. If an external condition is holding either ofthe lines low, the I2C engine enters the low-power SLEEP mode.


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A AS 0ADDR [6:0] CMD [7:0] Sr 1ADDR [6:0] A DATA [7:0] A DATA [7:0] PN

A AS A0 PADDR [6:0] CMD [7:0] DATA [7:0] DATA [7:0] A 66 sm

A AS 0ADDR [6:0] CMD [7:0] Sr 1ADDR [6:0] A DATA [7:0] A DATA [7:0] A

DATA [7:0] A DATA [7:0] PN

Waiting time inserted between incremental 2-byte write packet for a subcommand and reading results

(acceptable for 100 kHz)fSCL £

Waiting time inserted after incremental read

66 sm

66 sm

A AS 0ADDR [6:0] CMD [7:0] Sr 1ADDR [6:0] A DATA [7:0] A DATA [7:0] PN

A AS A0 PADDR [6:0] CMD [7:0] DATA [7:0] 66 sm

Waiting time inserted between two 1-byte write packets for a subcommand and reading results

(required for 100 kHz < f 400 kHz)SCL £

66 sm

A AS A0 PADDR [6:0] CMD [7:0] DATA [7:0] 66 sm

20




8.5.2.3 I2C Command Waiting TimeTo ensure proper operation at 400 kHz, a t(BUF) ≥ 66 μs bus-free waiting time must be inserted between allpackets addressed to the bq27531-G1 . In addition, if the SCL clock frequency (fSCL) is > 100 kHz, use individual1-byte write commands for proper data flow control. The following diagram shows the standard waiting timerequired between issuing the control subcommand the reading the status result. For read-write standardcommand, a minimum of 2 seconds is required to get the result updated. For read-only standard commands,there is no waiting time required, but the host must not issue any standard command more than two times persecond. Otherwise, the gauge could result in a reset issue due to the expiration of the watchdog timer.

Figure 11. I2C Command Waiting Time

8.5.2.4 I2C Clock StretchingA clock stretch can occur during all modes of fuel gauge operation. In SLEEP and HIBERNATE modes, a shortclock stretch occurs on all I2C traffic as the device must wake up to process the packet. In the other modes( BAT INSERT CHECK , NORMAL, SLEEP+ ) clock stretching only occurs for packets addressed for the fuelgauge. The majority of clock stretch periods are small as the I2C interface performs normal data flow control.However, less frequent yet more significant clock stretch periods may occur as blocks of Data Flash are updated.The following table summarizes the approximate clock stretch duration for various fuel gauge operatingconditions.

Table 4. I2C Clock StretchingGAUGINGMODE OPERATING CONDITION/COMMENT APPROXIMATE

DURATIONSLEEPHIBERNATE

Clock stretch occurs at the beginning of all traffic as the device wakes up. ≤ 4 ms

BAT INSERTCHECKNORMALSLEEP+

Clock stretch occurs within the packet for flow control (after a start bit, ACK or first data bit). ≤ 4 msNormal Ra table Data Flash updates. 24 msData Flash block writes. 72 msRestored Data Flash block write after loss of power. 116 msEnd of discharge Ra table Data Flash update. 144 ms


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R92.21k

1

2

J1

GND

Vin

1.0uFC5

U1BQ2419xRGE

1

2

3

4

5

6

7

8

9

10

11

12

24

23

22

21

20

19

18

17

16

15

14

13

PSEL

PG

STAT

BSCL

BSDA

OTG

CE

VBUS

PSEL

PG

STAT

SCL

SDA

INT

OTG

CE

ILIM

PwPd

VBUS

PMID

REGN

BTST

SW

SW

PGND

PGND

SYS

BAT

BAT

SYS

REGN

SW

SYS

BAT+

SYS

C1

10uF

C2

10uF

4.7uF C6

C747nF

10uFC8

L12.2uH

1 2

10uFC9

1uFC10

0.1uFC11

2

1

J5

System Output

GND

T 13P

1uFC14

10uFC132

5

R7

80.6kR2

169 R11100k

REGN

VCC

SYS SYS

CEOTG

SDA

PGSTAT

SYS

SCL R82.21k

Green GreenD1 D2R20 J 4P

1MΩ

R19J 3P

R1810.0k

R1710.0k

SDA

SCL

VSS

J101

2

3

4

VCC

SOC_INTSYS

VCC

SDA

SCL

SYS

SOC_INT

BSCL

BSDA

TS_GAUGE

TS_GAUGE

BAT+

Vin Max: 4.4V

Current max: 4A

PACK+

PACK-

T

J121

2

3

0.01

R24

0.1uFC19

0.1uFC16

U2BQ27531-G1YFF

E1

D1

B3

A3

E3

D3

C2

C1

E2

D2

A2

B2

C3

B1

A1

Only needed when theGauge is monitoring thebattery NTC.

C20

0.1uF

R25

1.00k

R22

18.2k

C18

0.033uF

R21

1.80M 1.0uF

C17

0.1uF

C15

10.0k

R23

SOC_INT

VSS

J131

2

REGIN

SCL

SDA

VCC

BI/TOUT

TS

VSS

VSS

BAT

CE

SOC_INT

BSCL

BSDA

SRN

SRP

T 2S

T 1S

1MΩ

21




9 Application and Implementation

NOTEInformation in the following applications sections is not part of the TI componentspecification, and TI does not warrant its accuracy or completeness. TI’s customers areresponsible for determining suitability of components for their purposes. Customers shouldvalidate and test their design implementation to confirm system functionality.

9.1 Application InformationThe fuel gauge can control a bq2419x Charger IC without the intervention from an application system processor.Using the bq27531-G1 and bq2419x chipset, batteries can be charged with the typical constant-current,constant-voltage (CCCV) profile or charged using a Multi-Level Charging (MLC) algorithm.

9.2 Typical Application

Figure 12. Typical Application Schematic


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22




Typical Application (continued)9.2.1 Design RequirementsSeveral key parameters must be updated to align with a given application's battery characteristics. For highestaccuracy gauging, it is important to follow-up this initial configuration with a learning cycle to optimize resistanceand maximum chemical capacity (Qmax) values prior to sealing and shipping systems to the field. Successfuland accurate configuration of the fuel gauge for a target application can be used as the basis for creating a"golden" gas gauge (.fs) file that can be written to all gauges, assuming identical pack design and Li-ion cellorigin (chemistry, lot, and so on). Calibration data is included as part of this golden GG file to cut down onsystem production time. If going this route, TI recommends averaging the voltage and current measurementcalibration data from a large sample size and use these in the golden file. Table 5 lists the items that must beconfigured to achieve reliable protection and accurate gauging with minimal initial configuration.

Table 5. Key Data Flash Parameters for ConfigurationNAME DEFAULT UNIT RECOMMENDED SETTING

Design Capacity 2425 mAh Set based on the nominal pack capacity as interpreted from cell manufacturer'sdatasheet. If multiple parallel cells are used, must be set to N × Cell Capacity.

Reserve Capacity-mAh 0 mAh Set to desired runtime remaining (in seconds/3600) × typical applied loadbetween reporting 0% SOC and reaching Terminate Voltage, if needed.

Cycle Count Threshold 900 mAh Set to 90% of configured Design Capacity.

Chem ID 1202 hex

Must be configured using TI-supplied Battery Management Studio software.Default open-circuit voltage and resistance tables are also updated inconjunction with this step. Do not attempt to manually update reported DeviceChemistry as this does not change all chemistry information. Always updatechemistry using the appropriate evaluation software tool.

Load Mode 0 — Set to applicable load model, 0 for constant current or 1 for constant power.Load Select 1 — Set to load profile which most closely matches typical system load.

Qmax Cell 0 2425 mAhSet to initial configured value for Design Capacity. The gauge will update thisparameter automatically after the optimization cycle and for every regularQmax update thereafter.

V at Chg Term Cell 0 4200 mV Set to nominal cell voltage for a fully charged cell. The gauge will update thisparameter automatically each time full charge termination is detected.

Terminate Voltage 3200 mV Set to empty point reference of battery based on system needs. Typical isbetween 3000 and 3200 mV.

Ra Max Delta 44 mΩ Set to 15% of Cell0 R_a 4 resistance after an optimization cycle is completed.

Charging Voltage 4200 mVSet based on nominal charge voltage for the battery in normal conditions(25°C, and so forth). Used as the reference point for offsetting by TaperVoltage for full charge termination detection.

Taper Current 121 mA Set to the nominal taper current of the charger + taper current tolerance toensure that the gauge will reliably detect charge termination.

Taper Voltage 100 mVSets the voltage window for qualifying full charge termination. Can be settighter to avoid or wider to ensure possibility of reporting 100% SOC in outerJEITA temperature ranges that use derated charging voltage.

Dsg Current Threshold 60 mA Sets threshold for gauge detecting battery discharge. Must be set lower thanminimal system load expected in the application and higher than Quit Current.

Chg Current Threshold 75 mASets the threshold for detecting battery charge. Can be set higher or lowerdepending on typical trickle charge current used. Also must be set higher thanQuit Current.

Quit Current 40 mA Sets threshold for gauge detecting battery relaxation. Can be set higher orlower depending on typical standby current and exhibited in the end system.

Avg I Last Run –299 mACurrent profile used in capacity simulations at onset of discharge or at all timesif Load Select = 0. Must be set to nominal system load. Is automaticallyupdated by the gauge every cycle.

Avg P Last Run –1131 mWPower profile used in capacity simulations at onset of discharge or at all timesif Load Select = 0. Must be set to nominal system power. Is automaticallyupdated by the gauge every cycle.

Sleep Current 10 mASets the threshold at which the fuel gauge enters SLEEP mode. Take care insetting above typical standby currents else entry to SLEEP may beunintentionally blocked.


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23




Typical Application (continued)Table 5. Key Data Flash Parameters for Configuration (continued)

NAME DEFAULT UNIT RECOMMENDED SETTINGCharge T0 0 °C Sets the boundary between charging inhibit and charging with T0 parameters.Charge T1 10 °C Sets the boundary between charging with T0 and T1 parameters.Charge T2 45 °C Sets the boundary between charging with T1 and T2 parameters.Charge T3 50 °C Sets the boundary between charging with T2 and T3 parameters.Charge T4 60 °C Sets the boundary between charging with T3 and T4 parameters.

Charge Current T0 50 % Des Cap Sets the charge current parameter for T0.Charge Current T1 100 % Des Cap Sets the charge current parameter for T1.Charge Current T2 100 % Des Cap Sets the charge current parameter for T2.Charge Current T3 100 % Des Cap Sets the charge current parameter for T3.Charge Current T4 0 % Des Cap Sets the charge current parameter for T4.Charge Voltage T0 262 16 mV Sets the charge voltage parameter for T0.Charge Voltage T1 262 16 mV Sets the charge voltage parameter for T1.Charge Voltage T2 259 16 mV Sets the charge voltage parameter for T2.Charge Voltage T3 256 16 mV Sets the charge voltage parameter for T3.Charge Voltage T4 0 16 mV Sets the charge voltage parameter for T4.

Chg Temp Hys 5 °C Adds temperature hysteresis for boundary crossings to avoid oscillation iftemperature is changing by a degree or so on a given boundary.

Chg DisabledRegulation V 4200 mV

Sets the voltage threshold for voltage regulation to system when charge isdisabled. TI recommends programming to same value as Charging Voltage andmaximum charge voltage that is obtained from Charge Voltage Tn parameters.

CC Gain 10 mΩCalibrate this parameter using TI-supplied evaluation software and calibrationprocedure in the TRM. Determines conversion of coulomb counter measuredsense resistor voltage to current.

CC Delta 10 mΩCalibrate this parameter using TI-supplied evaluation software and calibrationprocedure in the TRM. Determines conversion of coulomb counter measuredsense resistor voltage to passed charge.

CC Offset –1418 CountsCalibrate this parameter using TI-supplied evaluation software and calibrationprocedure in the TRM. Determines native offset of coulomb counter hardwarethat must be removed from conversions.

Board Offset 0 CountsCalibrate this parameter using TI-supplied evaluation software and calibrationprocedure in the TRM. Determines native offset of the printed-circuit-boardparasitics that must be removed from conversions.

Pack V Offset 0 mV

Calibrate this parameter using TI-supplied evaluation software and calibrationprocedure in the TRM. Determines voltage offset between cell tab and ADCinput node to incorporate back into or remove from measurement, dependingon polarity.


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24




9.2.2 Detailed Design Procedure

9.2.2.1 BAT Voltage Sense InputA ceramic capacitor at the input to the BAT pin is used to bypass AC voltage ripple to ground, greatly reducingits influence on battery voltage measurements. It proves most effective in applications with load profiles thatexhibit high-frequency current pulses (that is, cell phones) but is recommended for use in all applications toreduce noise on this sensitive high-impedance measurement node.

9.2.2.2 SRP and SRN Current Sense InputsThe filter network at the input to the coulomb counter is intended to improve differential mode rejection of voltagemeasured across the sense resistor. These components must be placed as close as possible to the coulombcounter inputs and the routing of the differential traces length-matched to best minimize impedance mismatch-induced measurement errors.

9.2.2.3 Sense Resistor SelectionAny variation encountered in the resistance present between the SRP and SRN pins of the fuel gauge will affectthe resulting differential voltage, and derived current, it senses. As such, TI recommends selecting a senseresistor with minimal tolerance and temperature coefficient of resistance (TCR) characteristics. The standardrecommendation based on best compromise between performance and price is a 1% tolerance, 100-ppm driftsense resistor with a 1-W power rating.

9.2.2.4 TS Temperature Sense InputSimilar to the BAT pin, a ceramic decoupling capacitor for the TS pin is used to bypass AC voltage ripple awayfrom the high-impedance ADC input, minimizing measurement error. Another helpful advantage is that thecapacitor provides additional ESD protection, because the TS input to system may be accessible in systems thatuse removable battery packs. The capacitor must be placed as close as possible to the respective input pin foroptimal filtering performance.

9.2.2.5 Thermistor SelectionThe fuel gauge temperature sensing circuitry is designed to work with a negative temperature coefficient-type(NTC) thermistor with a characteristic 10-kΩ resistance at room temperature (25°C). The default curve-fittingcoefficients configured in the fuel gauge specifically assume a 103AT-2 type thermistor profile and so that is thedefault recommendation for thermistor selection purposes. Moving to a separate thermistor resistance profile (forexample, JT-2 or others) requires an update to the default thermistor coefficients in data flash to ensure highestaccuracy temperature measurement performance.

9.2.2.6 REGIN Power Supply Input FilteringA ceramic capacitor is placed at the input to the fuel gauge internal LDO to increase power supply rejection(PSR) and improve effective line regulation. It ensures that voltage ripple is rejected to ground instead ofcoupling into the internal supply rails of the fuel gauge.

9.2.2.7 VCC LDO Output FilteringA ceramic capacitor is also needed at the output of the internal LDO to provide a current reservoir for fuel gaugeload peaks during high peripheral utilization. It acts to stabilize the regulator output and reduce core voltageripple inside of the fuel gauge.


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Temperature (qC)

fLO

SC

- L

ow F

requ

ency

Osc

illat

or (

kHz)

-40 -20 0 20 40 60 80 10030

30.5

31

31.5

32

32.5

33

33.5

34

D003Temperature (qC)

Rep

orte

d T

empe

ratu

re E

rror

(qC

)

-30 -20 -10 0 10 20 30 40 50 60-5

-4

-3

-2

-1

0

1

2

3

4

5

D004

Temperature (qC)

VR

EG

25 -

Reg

ulat

or O

utpu

t Vol

tage

(V

)

2.35

2.4

2.45

2.5

2.55

2.6

2.65

D001

VREGIN = 2.7 VVREGIN = 4.5 V

Temperature (qC)

f OS

C -

Hig

h F

requ

ency

Osc

illat

or (

MH

z)

-40 -20 0 20 40 60 80 1008

8.1

8.2

8.3

8.4

8.5

8.6

8.7

8.8

D002

25




9.2.3 Application Curves

Figure 13. Regulator Output Voltage vs Temperature Figure 14. High-Frequency Oscillator Frequency vsTemperature

Figure 15. Low-Frequency Oscillator Frequency vsTemperature

Figure 16. Reported Internal Temperature Measurement vsTemperature


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26




10 Power Supply Recommendations

10.1 Power Supply DecouplingBoth the REGIN input pin and the VCC output pin require low equivalent series resistance (ESR) ceramiccapacitors placed as close as possible to the respective pins to optimize ripple rejection and provide a stable anddependable power rail that is resilient to line transients. A 0.1-μF capacitor at the REGIN and a 1-μF capacitor atVCC will suffice for satisfactory device performance.

11 Layout

11.1 Layout Guidelines

11.1.1 Sense Resistor ConnectionsKelvin connections at the sense resistor are just as critical as those for the battery terminals themselves. Thedifferential traces must be connected at the inside of the sense resistor pads and not anywhere along the high-current trace path to prevent false increases to measured current that could result when measuring between thesum of the sense resistor and trace resistance between the tap points. In addition, the routing of these leadsfrom the sense resistor to the input filter network and finally into the SRP and SRN pins needs to be as closelymatched in length as possible else additional measurement offset could occur. It is further recommended to addcopper trace or pour-based "guard rings" around the perimeter of the filter network and coulomb counter inputs toshield these sensitive pins from radiated EMI into the sense nodes. This prevents differential voltage shifts thatcould be interpreted as real current change to the fuel gauge. All of the filter components need to be placed asclose as possible to the coulomb counter input pins.

11.1.2 Thermistor ConnectionsThe thermistor sense input must include a ceramic bypass capacitor placed as close to the TS input pin aspossible. The capacitor helps to filter measurements of any stray transients as the voltage bias circuit pulsesperiodically during temperature sensing windows.

11.1.3 High-Current and Low-Current Path SeparationFor best possible noise performance, it is extremely important to separate the low-current and high-current loopsto different areas of the board layout. The fuel gauge and all support components must be situated on one sideof the boards and tap off of the high-current loop (for measurement purposes) at the sense resistor. Routing thelow-current ground around instead of under high-current traces will further help to improve noise rejection.


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VSS

SOC

_IN

T

SRN

CE

SCL SRP

SDA

BSDA

VSS

TS

BI/TOUT

Vcc

REG

IN

BA

T

BSCL

SCL

SDA

INT

PACK –

BSDA

PACK+

10 mΩ 1%

C2

C3

C1

Kelvin connect SRP

and SRN

connections right at

Rsense terminals

Via connects to Power Ground

Kelvin connect the

BAT sense line right

at positive terminal to

battery pack

Use copper

pours for battery

power path to

minimize IR

losses

BSCL

To system host

processor

To charger slave

THERM

BATTERY PACK

CONNECTOR

Battery power

connection to

system

Ground return to

system

27




11.2 Layout Example

Figure 17. Layout Schematic


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28




12 Device and Documentation Support

12.1 Documentation Support

12.1.1 Related DocumentationTo obtain a copy of any of the following TI documents, go to the TI website at www.ti.com.• bq27531-G1 Technical Reference Manual User's Guide (SLUUA96)• bq27531EVM with bq27531 Battery Management Unit Impedance Track™ Fuel Gauge and bq24192 4.5-A,

Switch-Mode Battery Charger for Single-Cell Applications User's Guide (SLUUA90)

12.2 Community ResourcesThe following links connect to TI community resources. Linked contents are provided "AS IS" by the respectivecontributors. They do not constitute TI specifications and do not necessarily reflect TI's views; see TI's Terms ofUse.

TI E2E™ Online Community TI's Engineer-to-Engineer (E2E) Community. Created to foster collaborationamong engineers. At e2e.ti.com, you can ask questions, share knowledge, explore ideas and helpsolve problems with fellow engineers.

Design Support TI's Design Support Quickly find helpful E2E forums along with design support tools andcontact information for technical support.

12.3 TrademarksImpedance Track, MaxLife, NanoFree, E2E are trademarks of Texas Instruments.All other trademarks are the property of their respective owners.

12.4 Electrostatic Discharge CautionThese devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foamduring storage or handling to prevent electrostatic damage to the MOS gates.

12.5 GlossarySLYZ022 — TI Glossary.

This glossary lists and explains terms, acronyms, and definitions.

13 Mechanical, Packaging, and Orderable InformationThe following pages include mechanical, packaging, and orderable information. This information is the mostcurrent data available for the designated devices. This data is subject to change without notice and revision ofthis document. For browser-based versions of this data sheet, refer to the left-hand navigation.


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http://www.ti.com/corp/docs/legal/termsofuse.shtml

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http://e2e.ti.com

http://support.ti.com/

http://www.ti.com/lit/pdf/SLYZ022

PACKAGE OPTION ADDENDUM

www.ti.com 15-Jan-2016

Addendum-Page 1

PACKAGING INFORMATION

Orderable Device Status(1)

Package Type PackageDrawing

Pins PackageQty

Eco Plan(2)

Lead/Ball Finish(6)

MSL Peak Temp(3)

Op Temp (°C) Device Marking(4/5)

Samples

BQ27531YZFR-G1 ACTIVE DSBGA YZF 15 3000 Green (RoHS& no Sb/Br)

SNAGCU Level-1-260C-UNLIM -40 to 85 BQ27531

BQ27531YZFT-G1 ACTIVE DSBGA YZF 15 250 Green (RoHS& no Sb/Br)

SNAGCU Level-1-260C-UNLIM -40 to 85 BQ27531

(1) The marketing status values are defined as follows:ACTIVE: Product device recommended for new designs.LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.PREVIEW: Device has been announced but is not in production. Samples may or may not be available.OBSOLETE: TI has discontinued the production of the device.

(2) Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availabilityinformation and additional product content details.TBD: The Pb-Free/Green conversion plan has not been defined.Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement thatlead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used betweenthe die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above.Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weightin homogeneous material)

(3) MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.

(4) There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device.

(5) Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuationof the previous line and the two combined represent the entire Device Marking for that device.

(6) Lead/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish values may wrap to two lines if the finishvalue exceeds the maximum column width.

Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on informationprovided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken andcontinues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.

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http://www.ti.com/product/BQ27531-G1?CMP=conv-poasamples#samplebuy

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PACKAGE OPTION ADDENDUM


Addendum-Page 2

In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.

TAPE AND REEL INFORMATION

*All dimensions are nominal

Device PackageType

PackageDrawing

Pins SPQ ReelDiameter

(mm)

ReelWidth

W1 (mm)

A0(mm)

B0(mm)

K0(mm)

P1(mm)

W(mm)

Pin1Quadrant

BQ27531YZFR-G1 DSBGA YZF 15 3000 180.0 8.4 2.1 2.76 0.81 4.0 8.0 Q1

BQ27531YZFT-G1 DSBGA YZF 15 250 180.0 8.4 2.1 2.76 0.81 4.0 8.0 Q1

PACKAGE MATERIALS INFORMATION


Pack Materials-Page 1

*All dimensions are nominal

Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm)

BQ27531YZFR-G1 DSBGA YZF 15 3000 182.0 182.0 20.0

BQ27531YZFT-G1 DSBGA YZF 15 250 182.0 182.0 20.0

PACKAGE MATERIALS INFORMATION


Pack Materials-Page 2

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PACKAGE OUTLINE

C0.625 MAX

0.350.15

15X 0.350.25

1 TYP

2TYP

0.5TYP

0.5 TYP

B E A

D

4219381/A 02/2017

DSBGA - 0.625 mm max heightYZF0015DIE SIZE BALL GRID ARRAY

NOTES: 1. All linear dimensions are in millimeters. Any dimensions in parenthesis are for reference only. Dimensioning and tolerancing per ASME Y14.5M.2. This drawing is subject to change without notice.3. NanoFreeTM package configuration.

NanoFree Is a trademark of Texas Instruments.

BALL A1CORNER

SEATING PLANE

BALL TYP 0.05 C

A

1 3

0.015 C A B

SYMM

SYMM

C

2

B

D

E

SCALE 6.500

D: Max =

E: Max =

2.64 mm, Min =

1.986 mm, Min =

2.58 mm

1.926 mm

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EXAMPLE BOARD LAYOUT

15X ( 0.245)

(0.5) TYP

(0.5) TYP

( 0.245)METAL

0.05 MAX

SOLDER MASKOPENING

METAL UNDERSOLDER MASK

( 0.245)SOLDER MASKOPENING

0.05 MIN

4219381/A 02/2017


NOTES: (continued) 4. Final dimensions may vary due to manufacturing tolerance considerations and also routing constraints. For more information, see Texas Instruments literature number SNVA009 (www.ti.com/lit/snva009).

SYMM

SYMM

LAND PATTERN EXAMPLEEXPOSED METAL SHOWN

SCALE:30X

1 2

A

B

C

3

D

E

NON-SOLDER MASKDEFINED

(PREFERRED)

SOLDER MASK DETAILSNOT TO SCALE

EXPOSEDMETAL

SOLDER MASKDEFINED

EXPOSEDMETAL

www.ti.com

EXAMPLE STENCIL DESIGN

(0.5)TYP

(0.5) TYP

15X ( 0.25) (R0.05) TYP

METALTYP

4219381/A 02/2017


NOTES: (continued) 5. Laser cutting apertures with trapezoidal walls and rounded corners may offer better paste release.

SYMM

SYMM

SOLDER PASTE EXAMPLEBASED ON 0.1 mm THICK STENCIL

SCALE:40X

1 2

A

B

C

3

D

E

IMPORTANT NOTICE

Texas Instruments Incorporated (TI) reserves the right to make corrections, enhancements, improvements and other changes to itssemiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latest issue. Buyersshould obtain the latest relevant information before placing orders and should verify that such information is current and complete.TI’s published terms of sale for semiconductor products (http://www.ti.com/sc/docs/stdterms.htm) apply to the sale of packaged integratedcircuit products that TI has qualified and released to market. Additional terms may apply to the use or sale of other types of TI products andservices.Reproduction of significant portions of TI information in TI data sheets is permissible only if reproduction is without alteration and isaccompanied by all associated warranties, conditions, limitations, and notices. TI is not responsible or liable for such reproduceddocumentation. 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